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NOTICE DATE: March 25, 2021

NOTICE TYPE: M-A021721-02 Operations

SHORT DESCRIPTION: Retirement of Culberson Loop Remedial Action Scheme


DAYS AFFECTED: March 31, 2021

LONG DESCRIPTION: ERCOT has approved the proposal from Oncor Electric Delivery Company LLC (Oncor) to retire the Culberson Loop Remedial Action Scheme (RAS). The Culberson Loop RAS consists of redundant relays placed at every transmission switching station, wired to monitor the status of each transmission line terminal on the Culberson Loop. The RAS automatically performs remedial tripping in response to the specific contingencies of concern that may cause voltage instability. Oncor has indicated that the RAS is no longer required because the contingencies of concern do not result in voltage instability, due to 345kV transmission upgrades in the area.


Information regarding all RAS(s) can be found in the “Remedial Action Schemes and Constraint Management Plans” secure portlet located on the Market Information System (MIS) under the Transmission page of the Grid section.

Please review the ERCOT website for previous Market Notices related to the subject.

CONTACT: If you have any questions, please contact your ERCOT Account Manager. You may also call the general ERCOT Client Services phone number at (512) 248-3900 or contact ERCOT Client Services via email at [log in to unmask].

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